import sys
from PyQt5.QtWidgets import QWidget,QProgressBar,QPushButton,QApplication
from PyQt5.QtCore import QBasicTimer

class Example(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.pbar=QProgressBar(self)
        self.pbar.setGeometry(30,40,200,25)

        self.btn=QPushButton('Start',self)
        self.btn.move(40,80)
        self.btn.clicked.connect(self.doAction)

        self.timer=QBasicTimer()
        self.step=0

        self.setGeometry(300,300,280,170)
        self.setWindowTitle('ProgressBar')
        self.show()

    def timerEvent(self, e):
        if self.step>=100:
            self.timer.stop()
            self.btn.setText('Finished')
            return
        self.step=self.step+1
        self.pbar.setValue(self.step)

    def doAction(self):
        if self.timer.isActive():
            self.timer.stop()
            self.btn.setText('Start')
        else:
            self.timer.start(100,self)
            self.btn.setText('Stop')

if __name__=='__main__':
    app=QApplication(sys.argv)
    ex=Example()
    sys.exit(app.exec_())

